A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents

A61F2/02—Prostheses implantable into the body

A61F2/30—Joints

A61F2002/30001—Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof

A61F2002/30316—The prosthesis having different structural features at different locations within the same prosthesis; Connections between prosthetic parts; Special structural features of bone or joint prostheses not otherwise provided for

A61F2002/30331—Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements made by longitudinally pushing a protrusion into a complementarily-shaped recess, e.g. held by friction fit

A61F2002/30362—Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements made by longitudinally pushing a protrusion into a complementarily-shaped recess, e.g. held by friction fit with possibility of relative movement between the protrusion and the recess

A61F2002/30369—Limited lateral translation of the protrusion within a larger recess

A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents

A61F2/02—Prostheses implantable into the body

A61F2/30—Joints

A61F2002/30001—Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof

A61F2002/30316—The prosthesis having different structural features at different locations within the same prosthesis; Connections between prosthetic parts; Special structural features of bone or joint prostheses not otherwise provided for

A61F2002/30535—Special structural features of bone or joint prostheses not otherwise provided for

A61F2002/30574—Special structural features of bone or joint prostheses not otherwise provided for with an integral complete or partial collar or flange

A61F2220/0033—Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements made by longitudinally pushing a protrusion into a complementary-shaped recess, e.g. held by friction fit

Le but de cette invention est en conséquence de proposer une prothèse de cheville qui permette d'améliorer cette situation et d'obtenir une cinématique d'articulation qui se rapproche davantage de celle d'une cheville normale. The purpose of this invention is accordingly to provide a prosthetic ankle which allows to improve this situation and get a kinematic hinge which is closer to that of a normal ankle.

le jeu entre les surfaces latérales de butée est plus important dans la zone arrière d'une articulation équipée de la prothèse que dans sa zone avant ; the play between the lateral stop surfaces is greater in the rear area of ​​an articulation equipped with the prosthesis than in its front area;

le jeu entre les surfaces latérales de butée correspond à un débattement angulaire inférieur à 5° de part et d'autre d'une position médiane ; the play between the lateral stop surfaces corresponds to an angular displacement of less than 5 ° on either side of a median position;

chaque surface articulaire peut être définie comme étant engendrée par la rotation d'une ligne directrice plane comportant au moins un arc de cercle, autour d'au moins un axe contenu dans son plan et orienté obliquement par rapport au rayon moyen ou médian dudit arc de cercle ; each articular surface can be defined as being generated by the rotation of a plane guideline having at least one circular arc around at least an axis contained in its plane and obliquely oriented relative to the average or median radius of said arc of circle;

l'axe autour duquel on fait tourner la directrice, celle-ci étant supposée contenue dans un plan sensiblement vertical, monte en direction de la malléole interne du pied sur lequel la partie astragalienne est destinée à être fixée, en étant orienté vers le haut par rapport au rayon moyen ou médian de cette directrice ; the axis around which the directrix is ​​rotated, the latter being supposed contained in a substantially vertical plane, rises in the direction of the inner malleolus of the foot on which the astragalar part is designed to be fixed, being oriented upwardly compared to the average or median radius of this directrix;

la directrice est formée de trois arcs de cercle, un arc central et deux arcs latéraux, reliés par deux courbes présentant chacune un point d'inflexion ; directrix is ​​formed by three arcs of a circle, a central arc and two lateral arcs connected by two curves each having a point of inflexion;

la partie astragalienne de la prothèse comporte une partie articulaire latérale à double courbure, convexe suivant une direction avant-arrière et concave suivant une direction verticale, adaptée pour coopérer avec la partie adjacente de l'extrémité inférieure du péroné. the astragalar part of the prosthesis comprises a lateral joint part of double curvature, convex in a front-rear direction and concave in a vertical direction, adapted to cooperate with the adjacent part of the lower end of the fibula.

On voit sur la figure 1 les extrémités inférieures d'un tibia T et d'un péroné P, ainsi que l'astragale A située au voisinage des extrémités de ces deux os. Seen in Figure 1 the lower ends of a tibia T and P a fibula and the talus A located near the ends of those two bones.

Pour engendrer l'ensemble de la surface articulaire astragalienne, on fait tourner la directrice autour d'un axe X qui est contenu dans le plan de cette directrice et qui est orienté obliquement par rapport au rayon moyen ou rayon médian de la partie centrale 34a. To generate the set of the talar articular surface, the head is rotated about an axis X which is contained in the plane of the director and is oriented obliquely with respect to the mean radius or median radius of the central portion 34a.De préférence, l'angle α que forme cet axe avec le rayon médian est compris entre 70 et 85° et la distance entre le point I d'intersection de cet axe avec le rayon médian et la partie centrale de la directrice est de l'ordre de 10 à 24 mm. Preferably, the α angle formed by said axis with the median radius is between 70 and 85 ° and the distance between the point I of intersection of this axis with the median radius and the central portion of the director is in the order of 10 to 24 mm.

Ce jeu latéral autorise, par exemple, de part et d'autre d'une position moyenne, un débattement angulaire ± β de ± 2° autour du centre instantané de rotation qui est constitué par le centre O desdites surfaces d'appui latérales. This side clearance allows, for example, on either side of a mean position, an angular displacement of ± β ± 2 ° around the instantaneous center of rotation which is formed by the center O of said lateral bearing surfaces.L'angle β peut être compris entre 0 et 5°. The angle β can be between 0 and 5 °.

Une telle prothèse procure une cinématique qui est très proche de celle de l'articulation naturelle de la cheville et assure donc une bonne adequation entre le mouvement d'articulation procuré par les surfaces articulaires et les forces exercées par les ligaments. Such a prosthesis provides a kinematics which is very close to that of the natural ankle joint and thus ensures a good fit between the movement of articulation provided by the articular surfaces and the forces exerted by the ligaments.De plus, on réalise une bonne congruence entre les surfaces articulaires et un positionnement très favorables des centres instantanés de rotation dans tes différentes positions de la cheville. Moreover, we had a good congruence between the articular surfaces and a very favorable positioning of the instantaneous centers of rotation in your different positions of the ankle.

On peut ajouter que dans les cas où une prothèse de cheville doit être envisagée, il est fréquent que le calcanéum soit usé, ce qui se traduit chez le patient par un blocage du mouvement entre le talon et l'astragale. One might add that in cases where an ankle prosthesis should be considered, it is common that the calcaneus is used, which results in the patient by blocking the movement between the heel and the talus.La prothèse selon l'invention, grâce au jeu latéral limité qui est prévu, permet de compenser dans une large mesure cet inconvénient. The prosthesis according to the invention, thanks to the limited lateral clearance which is provided, is used to compensate to a large extent this disadvantage.

A titre de variante, on peut envisager de prévoir pour ce jeu angulaire latéral une valeur plus importante à l'arrière de l'articulation que dans sa partie avant. Alternatively, it is conceivable to provide for this lateral angular play a larger value at the back of the joint in its front part.C'est ainsi que ce jeu angulaire qui peut être de ± 2° dans la partie avant, peut augmenter jusqu'à ± 4 ou 5° dans la partie arrière. Thus, this angular play which may be ± 2 ° in the front portion, may increase to 4 or ± 5 ° in the rear portion.

De nombreuses variantes peuvent par ailleurs être apportées à cette prothèse, concernant notamment les modes d'ancrage sur le tibia et sur l'astragale, ainsi que la forme et la réalisation des pièces la constituant. Numerous variants may also be made to the prosthesis, in particular for anchoring modes on the tibia and the astragalus, and the shape and the realization of the component parts.

Dans la mesure où les surfaces articulaires présentent la courbure souhaitée, avec une concavité dirigée vers l'intérieur, elles peuvent être réalisées suivant des profils différents de celui représenté. To the extent that the joint surfaces have the desired curvature, with a concavity directed towards the inside, they can be carried out according to different profiles from the one shown.Par exemple, dans une première partie s'étendant de l'extrémité arrière jusqu'à deux tiers ou trois quarts de la longueur des surfaces articulaires, ces surfaces articulaires peuvent être engendrées comme décrit ci-dessus par rotation de la directrice autour de l'axe X, tandis que dans la zone avant restante, la surface peut être engendrée par rotation de cette même directrice autour d'un deuxième axe plus proche de la directrice et parallèle ou non à l'axe X. Dans ce cas, la courbure, en projection sur un plan sensiblement horizontal, est plus importante dans la partie avant que dans la partie arrière des surfaces articulaires. For example, in a first portion extending from the rear end to two thirds or three quarters of the length of the articular surfaces, the joint surfaces can be generated as described above by rotating the director around the axis X, while remaining in the front region, the surface may be generated by rotation of the same director about a second axis closer to the director and parallel or not to the axis X. in this case, the curvature, in projection on a substantially horizontal plane, is greater in the front part than in the rear portion of the articular surfaces.La position et l'inclinaison de ce deuxième axe sont alors choisies de façon à obtenir la courbure souhaitée et une transition harmonieuse avec la première partie de la surface. The position and inclination of the second axis are then chosen so as to obtain the desired curvature and a smooth transition with the first part of the surface.

Claims (14)

Ankle prosthesis, comprising a tibial part (10, 20)
and an astragalar part (30), each of which is provided with
means for securing, respectively on the lower end of a
tibia (T) and on the astragalus (A), and each delimiting an
articular surface (24, 34), the two articular surfaces
being formed such as to co-operate with one another and to
permit relative displacement between the two tibial and
astragalar parts around at least one axis, characterised in
that, taking as the reference direction the direction of
the axis of the tibia (T) on which the tibial part is
designed to be secured, seen in projection on a plane which
is substantially perpendicular to this reference direction,
the articular surfaces (24, 34) are curved, with concavity
which faces the inner malleolus (M) of the foot on which
the astragalar part is designed to be secured.

Ankle prosthesis according to claim 1, characterised
in that the articular surfaces (24, 34) each comprise a
central support surface (24a, 34a) and two lateral stop
surfaces (24d, 24e, 34d, 34e).

Ankle prosthesis according to claim 1, characterised
in that play is provided between the lateral stop surfaces
of the two articular surfaces, thus permitting limited
lateral clearance between these two articular surfaces.

Ankle prosthesis according to claim 3, characterised
in that the play between the lateral stop surfaces varies
along the length of the articular surfaces.

Ankle prosthesis according to claim 4, characterised
in that the play between the lateral stop surfaces is
greater in the rear area of an articulation equipped with
the prosthesis than in its front area.

Ankle prosthesis according to any one of claims 1 to
5, characterised in that the articular surfaces (24, 34)
each comprise a central surface (24a, 34a) and two lateral
support surfaces (24b, 24c, 34b, 34c), these two latter
being situated at levels which are different from that of
the central support surface, the lateral stop surfaces
(24d, 24e, 34d, 34e) consisting of areas of connection
between the central and lateral support surfaces.

Ankle prosthesis according to any one of claims 1 to
6, characterised in that each articular surface (24, 34)
can be defined as being generated by the rotation of a flat
guide line which comprises at least one arc of a circle,
around at least one axis (X) which is contained in its
plane and is oriented obliquely relative to the median or
mean radius of the said arc of a circle.

Ankle prosthesis according to claim 3 and claim 7,
characterised in that the play between the lateral stop
surfaces corresponds to an angular clearance (β) of less
than 5° on both sides of a median position.

Ankle prosthesis according to claim 7, characterised
in that the axis (X) around which the directrix is rotated,
the latter being assumed to be contained in a substantially
vertical plane, rises in the direction of the inner
malleolus (M) of the foot on which the astragalar part is
designed to be secured whilst being oriented upwards
relative to the median or mean radius of this directrix.

Ankle prosthesis according to claim 9, characterised
in that the said axis (X) forms an angle (α) of between 70
and 85° with the median or mean radius of the directrix.

Ankle prosthesis according to any one of claims 7 to
10, characterised in that the distance between the point of
intersection of the axis (X) of the articular surface
(24, 34) with the median or mean surface of the latter and
the central part (24a, 34a) of the directrix is between 10
and 24 mm.

Ankle prosthesis according to any one of claims 7 to
11, characterised in that the said directrix is formed by
three arcs of a circle, a central arc (24a; 34a) and two
lateral arcs (24b, 24c; 34b, 34c) which are connected by
two curves (24d, 24e; 34d, 34e) each of which has a point
of inflexion.

Ankle prosthesis according to any one of the preceding
claims, characterised in that seen in projection on the
plane which is perpendicular to the said reference
direction, the curvature of the articular surfaces is
greater in the front part of an articulation equipped with
the prosthesis than in its rear part.

Ankle prosthesis according to any one of the preceding
claims, characterised in that the astragalar part (30) of
the prosthesis comprises a lateral part (36) which delimits
an articular surface with a double curvature, which is
convex in a front-rear direction and concave in a vertical
direction, and is designed to co-operate with the adjacent
part (37) of the lower end of the fibula.